Electric discharge device



June 17, 1941. T. G. W D 2,246,125

ELECTRIC DISCHARGE DEVICE Filed April 1, 1941 v ITWVEETTtOTI by WWW/1 6. Kim/Maw; His Atteww ey,

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Patented June 17, 1941 2,248,125 ELECTRIC DISCHARGE DEVICE Thomas G. Crawford, Glenville, N. Y., assignor to General Electric New York ompany, a corporation of I Application April 1, 1941, Serial No. 386,350

4 Claims.

The present invention relates to improvements in enclosed electric devices of the type which includes a sealed'envelope and externally projecting terminal posts for connecting the device in an electrical circuit. Such devices are exemplifled by electronic discharge tubes, incandescent lamps and the like.

- In U. S. Patent, 2,069,638, granted February 2, 1937, in the name of D. K. Wright, there is described a form of enclosed electric device in which the terminal posts are constituted of hollow cup-like members enlarged at one end and joined at that end to the wall of the enclosing envelope of the device. The electric energytranslating elements within the envelope are supported from the various terminal posts by rigid conductors fixed internally to the smaller diameter portions of the posts. f

This type of terminal arrangement has proven eminently useful and has found wide acceptance. For certain uses, however, especially in connection with devices which during fabrication or use must be brought to very elevated temperatures, it is subject to certain difficulties. This is in part a result of the fact that the cup-like shape of the terminal posts makes it expedient to form them of a readily ductile metal tions to be distorted by the forces exerted on them by the energy-translating elements supported from the posts. In some instances, especially in multi-electrode discharge tubes, the

short-circuiting of the out sacrificing the inherent advantages of the type of terminal post under consideration. As will be explained more fully hereinafter, this is accomplished by the use of reinforcing means applied to the various terminal posts in such fashion as to buttress the more readily deformable wall parts from those components of the posts which are inherently of rigid character.

The features intended to be protected herein are pointed out with particularity in the appended claims. The invention itself may best be understood by reference to the following description taken in connection with the drawing in which Fig. 1 is a side elevation in partial section of a discharge tube suitably embodying the invention; Fig. 2 is an enlarged view of a fragmentary portion of Fig. 1, and Fig. 3 shows in perspective and in partial section one of the elements of Fig. 2.

Referring particularly to Fig. 1, there is shown a high power transmitting tube of the threeelectrode type. This includes an externally cooled anode comprising a tubular metal part I0 which is closed at one end and which merges at its other end into a reversely bent portion ll. The edge of the latter portion is sealed to a glass bulb l3 which in combination with the anode forms a vacuum-tight envelope. A flange member l5 joined to the reversely bent anode portion ll serves during use of' the tube to support the tube envelope and to connect it with a cooling jacket (not shown) for the anode.

At its upper end (in the inverted position shown) the glass bulb i3 terminates in a flat cap portion I! which bears a number of terminal posts, of which those shown are numbered 20 to 22 inclusive. Each of these posts is in the form of a cup-like member comprising an elongated tubular portion and a relatively enlarged end portion, these parts being respectively indicated for the post 22 at 22c and 22b in Fig. 2. It will be noted in connection with Fig. 2 that the part 2212 has a tapered edge and is sealed at that edge to a circular lip 24 which is pressed out of the glass cap I! and which surrounds an opening 25. At its other extremity the part 22b is joined to the part 22a by a transversely extending annular wall 26 which is formed integrally with both parts.

The posts 20 and 22 are, in the arrangement illustrated, employed as terminal connections for a grid structure supported within the interior of the anode ID. This structure includes a metal plate 28 which has an annular flange 29 struck up from its central section and which is supported on rigid conductors 3| and 32 soldered into the smaller tubular parts of the posts 20 and 22. The flange 29 bears a plurality of vertically extending rods 34 which serve as mounting elements for helically wound grid wires 36.

Within the interior of the grid structure there are provided a number of vertically extending cathode filaments 31 which are held in spaced relationship at their extremities by means of suitable mounting disks such as that shown at 38. The cathode structure thus formed is ener- I gized and supplied with current by means of appropriate lead-in conductors of which only one (numbered 40) is visible in Fig. 1. These conductors are supported at their extremities by enmetal disk 43 which is insulated from them and with the plate 28 so as completely to shield the tube base from heat and other harmful emanations from the electrode a readily ductile material such as copper. (This metal possesses a further qualification for this use in its high electrical conductivity.) However, it is observed that when copper is subjected to high temperatures, it tends to soften considerably volved in exhausting tubes such as that shown in Fig. '1, there is a tendency for the transverse wall parts corresponding to the part 26 (Fig. 2) to bend under the weight of the electrode structure supported within the tube. Under some circumstances this bending may be so great as to bring the cathode and grid into electrical contact, thus making the tube unusable.

In order to overcome the difficulties noted in the foregoing, my present invention provides for each of the terminal posts a reinforcing member in abutment with the transverse wall part of the post' for the purpose of minimizing the possibility of undesired flexion of that part. Thus, in connection with th post 22 (Fig. 2) a reinforcement of the type in question is shown as comprising an annular member 42 which is of tapered or wedge-shaped cross-section and which has its inner periphery bearing against the shank of the terminal post, and an adjacent surface in abutment with the wall part 26.

In applying the reinforcing member-42, which is preferably although not necessarily constituted of copper, it is slipped over the shaft of the part 22:; and secured to the external surface of the part 26 by means of a fused metal (e. g. silversoldered) joint.

Once in place, it provides a solid metal mass filling the angular space between the parts 26 and 22a, and effectively bracing the former from the latter. The rigidity of the resulting combination is such as to render it incapable of deformation except upon the application of a relatively great force.

The strength of the composite structure thusprovided is not materially lessened by the application of heat, and for this reason the structure is well adapted for use'in connection with devices to which high temperatures must be applied. In particular, multi-electrode tubes having terminal posts reinforced in'the manner described have been found to be substantially free from difllculties arising through loss of'alignment of the electrodes during the exhaust treatment.

while the invention has been described by reference to a particular embodiment thereof it will be understood that numerous modifications may be made bythose skilledin the art without actually departing from the invention. I, theresuch equivalent variations as come within the true spirit and scope of the foregoing disclosure.

, fore, aim in the appended claims to cover all What I claim as new and desire to secure by Letters Patent of the United States is: 1.-'An electric device comprising an envelope having a glass wall with an opening therein, a

hollow metal terminal having an enlarged end portion which is sealed to the glass wall in a region surrounding said opening, said terminal post also including a terminal-forming portion of relatively smaller diameter which is joined to said enlarged end portion by an annular transversely extending wall part, electric energytranslating means within said envelope, a member supporting said means at least in part from said terminal-forming portion of the terminal post, and separate reinforcing means abutting said transversely extending wall part for preventing flexion thereof due to forces exerted thereon by said energy-translating means.

2. An electric device comprising an envelope containing electric energy-translating means, an externally projecting hollow terminal post constituted of metal of relatively ductile character and having an enlarged end portion which is terminally sealed into the wall of the envelope,

the terminal post'also including a second terminal-forming portion of smaller diameter which is joined to said end portion by a transversely extending wall part formed integrally with both portions, means providing a substantially rigid connection within the envelope between said energy-translating means and the said second portion of the terminal'post, and a body of metal filling th external angular space between saidsecond portion of the terminal post and said transversely extending wall part; thereby effectively bracing the latter from the former so as to prevent. distortion of the said wall part due to forces exerted by the energy-translating means,

3. In an electric device of a type required to be subjected to elevated temperatures during the fabrication or use thereof, the combination which includes an envelope having a glass wall with an opening therein, an externally projecting hollow terminal post having an enlarged end portion sealed to the said glass wall in a region surrounding said opening, said terminal post also including a terminal-forming portion of relatively smaller diameter, which is joined to said enlarged end portion by an annular transversely extending wall part formed integrally with both the aforesaidportions, electric energy-translating means within said envelope, a member supporting said energy-translating means at least in part from the terminal-forming portion of said-post, and an annular metal member closely surrounding said terminal-forming portion and externally joined by a fused metal joint to said transversely extending wall part by forces exerted on it by said energy-translating means, said reinforcing means comprising an annular member of wedge-shaped cross-section having one surface bearing against said second post portion and an adjoining surface abutting said transversely extending wall part.

THOMAS CRAWFORD. 

